EP2614249B1 - Method and device for controlling an internal combustion engine - Google Patents

Description

State of the art

In particular, in vehicles with start / stop technology, that is, when the engine is often switched off and on again during normal driving, a comfortable outlet of the internal combustion engine and a quick restart of the internal combustion engine is of great importance.

The JP-2008298031 A describes a method in which the throttle of the internal combustion engine is closed in the outlet to suppress vibrations. By this measure, the air charge in the cylinders in the internal combustion engine is reduced, thus reducing the roughness of the spout, since compression and decompression are minimized.

For the restart of the internal combustion engine, however, as much air in the cylinders, in which is ignited for the restart required. One is therefore in a conflict of objectives between a fast engine start (which requires a lot of air in the cylinder) and a comfortable, that is low-vibration engine spout (which requires little air in the cylinder). This conflict of objectives is resolved by the present invention.

For example, as generally known in the art, see EP 1 582 738 A2 are devices that change the stroke course in particular of the intake valves of the internal combustion engine, and thus provide the air filling of the cylinder. In particular, it is known that the stroke profile of the intake valves can be varied as desired by electrohydraulic actuators. Internal combustion engines with such an electro-hydraulic valve adjustment do not require a throttle valve. It is also known that the stroke course in particular of the intake valves by an adjustment the camshaft can be varied. Such devices as well as the throttle valve, with which the air filling of the cylinder can be changed, are referred to below as Luftdosiereinrichtungen.

Disclosure of the invention

If, with the aid of an air dosing device, an amount of air supplied to the internal combustion engine is reduced, and only increased again shortly before a standstill of the internal combustion engine, so-called engine shaking, ie the noticeable generation of vibrations, can be avoided. This is achieved in that in the outlet of the internal combustion engine, the amount of air supplied to the engine is first reduced, and then, when a detected speed of the internal combustion engine has fallen below a speed threshold, is increased again.

An intake cylinder that is in an intake stroke immediately after or during the increase in the amount of air supplied is then supplied with an increased amount of air, and then has an increased air charge. If this intake cylinder now goes into a compression stroke, the increased air charge as a gas spring, which exerts a strong restoring torque via the intake cylinder ZYL2 crankshaft. Conversely, the respective air charge in the cylinders, which are going down, exerts a torque on the crankshaft that acts in the direction of forward rotation of the crankshaft. Since these cylinders, which are moving in a downward movement, have a low air charge, a restoring torque acts on the crankshaft as a whole.

If the speed threshold value is selected appropriately, it can be ensured that the intake cylinder no longer goes into a power stroke after the increased air quantity has been increased. This has the advantage that compression of the increased air charge is avoided, which prevents unwanted vibrations.

It is particularly advantageous if the rotational speed threshold value is selected such that the inlet cylinder no longer goes into the power stroke after the increased amount of air has been increased. If the speed threshold is selected and if the engine speed is greater than the engine speed threshold, when a re-start request is determined, a method of restarting the engine particularly quickly can be realized.

In order to robustly select the speed threshold value in such a way that the inlet cylinder, after the increase in the metered amount of air, is no longer in the power stroke, an adaptation method is proposed according to the invention. For this purpose, it is necessary to define suitable criteria in which the speed threshold value is reduced or increased.

If the speed threshold value is reduced, if the inlet cylinder still passes a top dead center after the increase in the metered amount of air and before the engine is stopped, it is ensured in a particularly simple manner that vibrations in the further operation of the internal combustion engine due to the inadmissible passing through a top dead center at high Air filling are prevented.

If the speed threshold value is increased when the intake cylinder no longer enters a compression stroke after the increased air quantity has been increased, it is ensured in a particularly simple manner that the intake cylinder shows a pendulum behavior during the further operation of the internal combustion engine.

If the speed threshold value is changed as a function of a return pendulum angle, it can be ensured in a particularly simple manner that the inlet cylinder exhibits a defined pendulum behavior in the future operation of the internal combustion engine.

If the speed threshold value is increased when the return pendulum angle is smaller than a predefinable minimum return pendulum angle, it is achieved that the intake cylinder is particularly robust, the top dead center just not reached.

If the speed threshold value is increased to a predefinable initial threshold value, then the adaptation method according to the invention has defined entry points, and thus it is particularly robust.

If the initial threshold value chosen so large that the inlet cylinder passes through top dead center safely, it is achieved that the speed threshold value ns is always adapted coming from too large values, which makes the adaptation process particularly simple.

The monitoring of the speed of the internal combustion engine is easiest at the dead centers. If it is determined at a dead center that the speed has fallen below the speed threshold, then the intake cylinder is just in the intake stroke. When the amount of air metered by the air metering device is increased while the exhaust valve of the intake cylinder is opened, an increased amount of air is pumped from a suction pipe into an exhaust pipe. This leads to disadvantageous noise development. On the other hand, if the amount of air metered in by the air metering device is increased too late during the intake stroke of the intake cylinder, a high pressure gradient results between the intake pipe and the cylinder. The inflow of air in this case leads to significant unwanted noise. In order to minimize this noise development, it is advantageous if the air quantity metered by the air metering device is increased immediately after the end of the valve overlap of the intake cylinder, ie immediately after the closing of the exhaust valve.

Since the internal combustion engine is stopped, the injection of fuel is switched off. For a quick restart of the internal combustion engine this is disadvantageous because no ignitable mixture is present in the cylinders. Since in the method according to the invention air is led from the intake manifold into the intake cylinder, with suitable injection before the end of the intake stroke it can be ensured that an ignitable fuel / air mixture is present in the intake cylinder. Since the intake cylinder comes to a halt near a bottom dead center or in the compression stroke, this is very advantageous for a quick restart, since a starter only has to perform a rotation of 180 ° of the crankshaft until it can be ignited in the intake cylinder.

If the fuel is injected before or immediately after the intake cylinder goes into the intake stroke, this is particularly favorable for mixture formation. With intake manifold injection, the metered amount of fuel can be metered very finely, in direct injection, the early injection of fuel is advantageous for the turbulence of air and fuel.

Figur 1

die Darstellung eines Zylinders einer Brennkraftmaschine ,

Figur 2

schematisch den Verlauf einiger Kenngrößen der Brennkraftmaschine beim Stoppen der Brennkraftmaschine,

Figur 3

den Ablauf des erfindungsgemäßen Verfahrens zum Stoppen der Brennkraftmaschine,

Figur 4

einen Drehzahlverlauf beim Stoppen und Wiederstart der Brennkraftmaschine,

Figur 5

detailliert den Drehzahlverlauf beim Stoppen und Wiederstart der Brennkraftmaschine,

Figur 6

den Ablauf des erfindungsgemäßen Verfahrens beim Wiederstart der Brennkraftmaschine,

Figur 7

schematisch ein Auspendelverhalten der Brennkraftmaschine bei verschiedenen Drehzahlschwellenwerten,

Figur 8

den Ablauf des erfindungsgemäßen Verfahrens zur Bestimmung des Drehzahlschwellenwerts.

Hereinafter, embodiments of the invention will be explained in more detail with reference to the accompanying drawings. In the drawing show:

FIG. 1

the representation of a cylinder of an internal combustion engine,

FIG. 2

schematically the course of some characteristics of the internal combustion engine when stopping the internal combustion engine,

FIG. 3

the sequence of the method according to the invention for stopping the internal combustion engine,

FIG. 4

a speed curve when stopping and restarting the internal combustion engine,

FIG. 5

detailed the speed curve when stopping and restarting the internal combustion engine,

FIG. 6

the sequence of the method according to the invention when restarting the internal combustion engine,

FIG. 7

schematically a Auspendelverhalten the internal combustion engine at different speed thresholds,

FIG. 8

the sequence of the method according to the invention for determining the speed threshold value.

Description of the embodiments

FIG. 1 shows a cylinder 10 of an internal combustion engine with a combustion chamber 20, a piston 30 which is connected to a connecting rod 40 with a crankshaft 50 is. The piston 30 performs in a known manner by an upward and downward movement. The reversal points of the movement are called dead centers. The transition from upward movement to downward movement is referred to as top dead center, and the transition from downward movement to upward movement is referred to as bottom dead center. An angular position of the crankshaft 50, a so-called crankshaft angle, is defined in a conventional manner relative to top dead center. A crankshaft sensor 220 detects the angular position of the crankshaft 50.

Via a suction pipe 80, air to be burned is sucked into the combustion chamber 20 in a known manner during a downward movement of the piston 30. This is referred to as intake stroke or intake stroke. Via an exhaust pipe 90, the burned air is forced out of the combustion chamber 20 during an upward movement of the piston 30. This is commonly referred to as outlet stroke. The amount of air sucked in via the intake pipe 80 is adjusted via an air metering device, in the exemplary embodiment a throttle valve 100 whose position is determined by a control unit 70.

Through a suction pipe injection valve 150, which is arranged in the intake pipe 80, fuel is injected into the air sucked from the intake pipe 80 and a fuel-air mixture in the combustion chamber 20 is generated. The amount of fuel injected through the port injection valve 150 is determined by the controller 70, typically over the duration and / or magnitude of a drive signal. A spark plug 120 ignites the fuel-air mixture.

An intake valve 160 at the inlet of the intake pipe 80 to the combustion chamber 20 is driven by cams 180 from a camshaft 190. Also, an exhaust valve 170 at the inlet of the exhaust pipe 90 to the combustion chamber 20 via cams 182 may be driven by the camshaft 190. The camshaft 190 is coupled to the crankshaft 50. Typically, the camshaft 190 makes one revolution per two revolutions of the crankshaft 50. The camshaft 190 is configured such that the exhaust valve 170 opens in the exhaust stroke and closes near the top dead center. The intake valve 160 opens near top dead center and closes in the intake stroke. A phase in which exhaust valve 170 and inlet valve of a technique open simultaneously are referred to as valve overlap. Such a valve is used for example for internal exhaust gas recirculation. In particular, the camshaft 190 can be designed so as to be controllable by the control unit 70, so that depending on the operating parameters of the internal combustion engine, different stroke profiles of the inlet valve 160 and the outlet valve 170 can be set. Likewise, however, it is also possible that the intake valve 160 and the exhaust valve 170 are not moved up and down via the camshaft 190 but via electrohydraulic valve actuators. In this case, the camshaft 190 and the cams 180 and 182 may be omitted. Likewise, in such electro-hydraulic valve actuators, the throttle valve 100 is not necessary.

A starter 200 is mechanically connectable via a mechanical coupling 210 with the crankshaft 50. Establishing the mechanical connection between starter 200 and crankshaft 50 is also referred to as Einspuren. The release of the mechanical connection between starter 200 and crankshaft 50 is also referred to as dropping. The meshing is only possible if the speed of the internal combustion engine is below a dependent of the engine and the starter speed threshold.

FIG. 2 shows the behavior of the internal combustion engine when stopping the internal combustion engine. FIG. 2a shows the sequence of different clocks of a first cylinder ZYL1 and a second cylinder ZYL2, plotted against the angle of the crankshaft KW. Registered are a first dead center T1, a second dead center T2, a third dead center T3, a fourth dead center T4 and a fifth dead center T5 of the internal combustion engine. Between these dead centers, the first cylinder ZYL1 passes in a known manner the exhaust stroke, the intake stroke, a compression stroke and a power stroke. In the embodiment of an internal combustion engine with four cylinders, the clocks of the second cylinder ZYL2 are shifted by 720 ° / 4 = 180 °. With respect to the first cylinder ZYL1, the first dead center T1, the third dead center T3 and the fifth dead center T5 are bottom dead centers, the second dead center T2 and the fourth dead center T4 are top dead centers. With respect to the second cylinder ZYL2, the first dead center T1, the third dead center T3 and the fifth dead center T5 are top dead centers, the second dead center T2 and the fourth dead center T4 are bottom dead centers.

FIG. 2b shows parallel to the in FIG. 2a shown cycles the course of a speed n of the internal combustion engine over time t. The speed n is defined, for example, as the time derivative of the crankshaft angle KW. The first dead center T1 corresponds to a first time t1, the second dead center T2 corresponds to a second time t2, the third dead center T3 corresponds to a third time t3, and the fourth dead center T4 corresponds to a fourth time t4. Between every two successive points in time, for example between the first time t1 and the second time t2, the speed initially increases briefly, in order then to drop monotonically. The short speed increase is due to the compression of the air charge in the cylinders. A cylinder, which passes through a top dead center, compresses its maximum air charge, so that it is stored in compression energy. This compression energy is partially converted into rotational energy during further rotation of the internal combustion engine.

Figure 2c shows parallel to Figure 2a and 2b the timing of a drive signal DK of the throttle valve 100. As known from the prior art, the throttle valve 100 is initially closed when stopping the engine, which corresponds to a first drive signal DK1. Falls like in FIG. 2b illustrated the speed n of the internal combustion engine below a speed threshold value ns, for example 300 U / min, the throttle valve 100 is opened according to the invention at an opening time tauf, which corresponds to a second drive signal DK2. The opening time tauf is chosen so that it occurs shortly after the third dead center T3, which is the next dead center, after the engine speed n has fallen below the speed threshold value ns. The second cylinder ZYL2 goes to the third dead center T3 in the intake stroke. It is therefore also referred to below as the inlet cylinder ZYL2. In the embodiment, the opening time tauf coincides with the end of the valve overlap of the intake cylinder, that is, with the timing of closing the exhaust valve 170 of the intake cylinder ZYL2. With respect to the top dead center of the intake cylinder ZYL2, the opening timing tauf corresponds to an opening crankshaft angle KWauf. To determine the time at which the speed n of the internal combustion engine below the speed threshold ns has fallen, the speed n of the internal combustion engine can be monitored either continuously. Since the increase in the rotational speed n of the internal combustion engine after the dead centers is small, and the opening time tauf should be shortly after a dead center, but it is also possible to check at each dead center of the internal combustion engine, whether the speed n of the internal combustion engine below the speed threshold ns fallen is. Im in FIG. 2b illustrated embodiment, it is detected at the first time t1 and the second time t2 that the speed n of the internal combustion engine has not fallen below the speed threshold ns. At the third time t3, it is detected for the first time that the engine speed n has fallen below the speed threshold ns, and the throttle valve 100 is opened.

Through the opening of the throttle valve 100, a lot of air flows into the intake cylinder in the intake stroke. If the intake cylinder ZYL2 after the fourth time t4 in the compression stroke, so prevails at the compared to the remaining cylinders greatly increased air charge compression work to be released in the expanding cylinders compression energy, and the speed n of the engine drops quickly until they come to a Returning time tosc drops to zero. The rotational movement of the crankshaft 50 now rotates, and the engine speed n becomes negative. The return period tosc corresponds to a FIG. 2a drawn Rückpendelwinkel RPW the crankshaft 50. At a stop time t stop the engine stops. It should be noted that the representation of the time axis is nonlinear. Corresponding to the drop in the rotational speed n of the internal combustion engine, the time interval between the third time t3 and the fourth time t4 is greater than the time interval between the second time t2 and the third time t3, which in turn is greater than the time interval between the first time t1 and the second time t2. The fifth dead center T5 of the internal combustion engine is not reached. In the time interval between the return pendulum time tosc and the stop time tstopp, the crankshaft 50 executes a pendulum motion in which the second cylinder ZYL2 oscillates in its compression stroke and its intake stroke, the first cylinder ZYL1 correspondingly in its power stroke and compression stroke.

FIG. 3 shows the sequence of the procedure, which corresponds to the in FIG. 2 corresponds to illustrated behavior. When the internal combustion engine is running, it is determined in a stop detection step 1000 that the internal combustion engine should be issued. Step 1010 follows by shutting off injection and ignition. The internal combustion engine is thus in the outlet. Subsequently, step 1020 follows in which the throttle valve is closed. In internal combustion engines with camshaft adjustment, alternatively, a switchover to a smaller cam can take place in step 1020, so that the air charge in the cylinders is reduced. In internal combustion engines with electrohydraulic valve timing, the valves of the internal combustion engine can be closed in step 1020. This is followed by step 1030, in which it is checked whether the speed n of the internal combustion engine has fallen below the speed threshold value ns. If this is the case, step 1040 follows. If this is not the case, step 1030 is repeated until the speed n of the internal combustion engine has fallen below the speed threshold value ns. In step 1040, the throttle valve 100 is opened at the opening timing tauf. In internal combustion engines with camshaft adjustment, instead, in step 1040, for example, be switched to a larger cam, so that the air charge increases in the intake cylinder ZYL2. In electrohydraulic valve timing engines, in step 1040, the intake valve 160 of the intake cylinder ZYL2 may be controlled to be open during the intake stroke of the intake cylinder ZYL2, thus increasing the air charge in the intake cylinder ZYL2. Step 1060 follows. In optional step 1060, fuel is injected into the intake manifold 80 of the engine via the port injection valve 150. This injection of fuel is carried out so that in the intake stroke, a fuel / air mixture is sucked into the intake cylinder ZYL2. In step 1100, the inventive method ends. As in FIG. 2b illustrates, the internal combustion engine oscillates in a standstill position, in which the inlet cylinder ZYL2 comes to stand in the intake stroke or in the compression stroke. Injection of fuel in step 1060 is advantageous to an intake manifold injection internal combustion engine for a quick restart of the engine.

FIG. 4 shows the time course of the speed n of the internal combustion engine when stopping and restarting. The speed n of the internal combustion engine falls during a phase-out phase T_outflow in the in FIG. 2b illustrated way, and changes Finally, the sign when the rotational movement of the internal combustion engine to in FIG. 2b illustrated return pendulum time tosc reverses. This is in FIG. 4 represented as the end of the phase-out phase T_output and beginning of a pendulum phase T_Pendel. Even during the phase-out phase T_outrun, it is determined at a start-up desired time tstart that the internal combustion engine should be restarted, for example because it was detected that a driver pressed an accelerator pedal. Such a determined start request before the stop time tstopp is also referred to as "change of mind". In the pendulum phase T_Pendel the course of the speed n of the internal combustion engine performs a resulting course until it reaches the in FIG. 2b illustrated stop time t stop falls to zero and stays there. The stop time tstopp marked in FIG. 4 the end of the pendulum phase T_Pendel.

In the known in the prior art method for starting the internal combustion engine is detected after the pendulum phase T_Pendel that the internal combustion engine is stationary, the starter 200 is meshed, and the starter driven. After a in FIG. 4 Not shown Ansteuertotzeit T_tot of the starter 200 of, for example, 50ms starts the starter 200 at a time tSdT a rotational movement and thus sets the crankshaft 50 in motion again. In contrast, in the method according to the invention a first Einspurzeitpunkt tein1 and optionally a second Einspurzeitpunkt tein2 is determined. The first Einspurzeitpunkt tein1 and the second Einspurzeitpunkt tein2 are characterized in that the speed n of the internal combustion engine is so low that the starter 200 can be eingespurt. The first Einspurzeitpunkt tein1 and the second Einspurzeitpunkt tein2 are determined by the controller 70. If the time interval between the start desired time tstart and the first Einspurzeitpunkt tein1 greater than the Ansteuertotzeit T tot, the starter 200 is meshed and driven so that it starts a rotational movement for the first Einspurzeitpunkt tein1. If the first Einspurzeitpunkt tein1 time too close to the start-desired time tstart, the starter 200 is meshed and driven so that it starts a rotational movement to the second Einspurzeitpunkttein2.

FIG. 5 illustrates in detail the choice of the first Einspurzeitpunktts tein1 and the second Einspurzeitpaints tein2. As described, the speed n of the internal combustion engine drops after the opening time tauf rapidly down to zero, and the internal combustion engine starts at the return time t_osc a backward movement. The first Einspurzeitpunkt tein1 is determined after opening the throttle valve 100, for example, based on maps or based on stored in the control unit 70 models and corresponds to the estimated Rückpendelzeitpunkt tosc. Of course, it is also possible that instead of the return time tosc other times, to which the speed n of the internal combustion engine has a zero crossing, are predicted, and be selected as the first Einspurzeitpunkt tein1.

In addition to the zero crossing of the speed n of the internal combustion engine, a second Einspurzeitpunkt tein2 can be selected, from which it is ensured that the speed n of the internal combustion engine no longer leaves a speed band in which a meshing of the starter 200 is possible. This speed band is given, for example, by a positive threshold nplus, for example 70 revolutions per minute, up to which the starter 200 can be meshed in a forward rotation of the internal combustion engine, and by a negative threshold nminus, for example 30 rpm, up to that of the starter 200 can be eingespurt in a reverse rotation of the internal combustion engine. The control unit 70 calculates, for example based on maps, that the kinetic energy of the internal combustion engine from the second Einspurzeitpunkt tein2 has dropped so far that the speed band [nminus, nplus] will not leave. At the second Einspurzeitpunkt tein2 or at any time after the second Einspurzeitpunkt tein2 the starter 200 and can be meshed and placed in a rotary motion.

FIG. 6 shows the sequence of the inventive method for restarting the internal combustion engine. Step 2000 coincides with the in FIG. 3 step 1000. In it a request to stop the internal combustion engine, determined. Step 2005 follows. In step 2005, the throttle is closed, or other measures, such as adjustment of the cams 180, 182, or appropriate electrohydraulic actuation of the valves 160 and 170, are taken to reduce the air charge in the cylinders. It follows step 2010.

In step 2010, it is determined whether during the outflow of the internal combustion engine, ie during the in FIG. 4 Outflow phase T_output a start request for starting the internal combustion engine is determined. If this is the case, step 2020 follows. If this is not the case, step 2090 follows. In step 2020, it is checked whether the engine speed n (possibly by a minimum distance, for example 10 revolutions per minute) is above the speed threshold value ns. These checks can be done continuously, or crankshaft synchronous, in particular to each dead center of the internal combustion engine. If the speed n of the internal combustion engine is above the speed threshold value ns, then step 2030 follows, otherwise step 2070 follows.

In step 2030, the throttle is opened, or other measures, e.g. Adjusting the cams 180, 182 or a suitable electrohydraulic control of the valves 160 and 170, taken to increase the air charge in the cylinder, which is next in the intake stroke. Fuel is injected into intake manifold 80 via intake manifold injector 50. This is followed by step 2040, in which the intake cylinder ZYL2 is determined, that is, the cylinder whose air charge substantially increases next in the intake stroke. The intake cylinder ZYL2 goes into the intake stroke and sucks the fuel / air mixture, which is located in the intake manifold 80. Subsequently, the inlet cylinder ZYL2 goes into the compression stroke. The speed n is greater than the speed threshold ns. The speed threshold value ns is selected such that the intake cylinder ZYL2 is no longer going through a top dead center. At the rotational speed n of the internal combustion engine, it is therefore ensured that the intake cylinder ZYL2 again passes through a top dead center and transitions into the power stroke. Step 2050 follows. In step 2050, the fuel / air mixture in the intake cylinder ZYL2 is ignited, which accelerates the rotation of the crankshaft 50, and step 2060 follows. In step 2060, further measures are taken to start the engine to accomplish, in particular, a fuel / air mixture is ignited in the other cylinders of the internal combustion engine accordingly. With the start of the internal combustion engine, the inventive method ends.

In step 2070, fuel is injected into the draft tube 80 via the port injection valve 150. It follows step 2100.

In step 2090, according to the FIG. 3 Step 1030 checks whether the rotational speed n of the internal combustion engine has fallen below the rotational speed threshold value ns. If this is not the case, the method branches back to step 2010. If this is the case, step 2100 follows.

Step 2100 corresponds to step 1040 of FIG FIG. 3 , The throttle valve is opened or another Luftdosiereinrichtung, for example, a cam adjustment or an electro-hydraulic valve control, so controlled that the amount of air supplied is increased. It follows step 2110.

In step 2110, it is determined whether there is a request to start the engine. If so, step 2120 follows. If not, step 2110 is repeated until there is a request to start the engine. In step 2120, it is checked whether the internal combustion engine is stationary. This corresponds to the in FIG. 4 shown period after the end of the pendulum phase T_Phase. If this is the case, then step 2060 follows, in which conventional measures for starting the internal combustion engine are carried out. As in FIG. 4 the internal combustion engine is started at a time tSdT.

If the internal combustion engine is not at a standstill in step 2120, step 2150 follows. In step 2150, the first meshing time tein1 is predicted. This prediction is done, for example, using a map. Based on the rotational speed n, the intake cylinder ZYL2 was determined in the last run of a top dead center (in the embodiment at the fourth time t4), the kinetic energy of the internal combustion engine can be determined, from the second position DK2 of Luftdosiereinrichtung the air filling of the intake cylinder ZYL2, and thus the magnitude of the gas spring compressed by the intake cylinder ZYL2 in the compression stroke can be estimated. From this it is possible to estimate the return oscillation time tosc, which is predicted as the first Einspurzeitpunkt tein1. It is followed by step 2160, in which it is checked whether the time difference between the first Einspurzeitpunkt tein1 and the current time is greater than the Ansteuertotzeit T_tot of the starter 200. If so, step 2170 follows. If not, step 2180 follows.

In step 2180, the second meshing time tein2 is determined. As in FIG. 5 explains, the second Einspurzeitpunkt tein2 is selected so that the rotational speed n of the internal combustion engine from the second Einspurzeitpunkt tein2 remains in the speed interval between the negative threshold nminus and the positive threshold nplus. In the following step 2190, the starter 200 is meshed and started from the second Einspurzeitpunkt tein2. This is followed by step 2060, in which the further measures for starting the internal combustion engine are performed. Alternatively, it is also possible to determine in step 2180 a one-track interval during which the speed n remains between the negative threshold nminus and the positive threshold nplus. In step 2190, in this case, the starter 200 is meshed and started at the one-track interval.

Instead of a suction pipe injection valve 150, it is also conceivable that the injection valves of the internal combustion engine is arranged in the combustion chamber, that is configured as a direct injection valve. In this case, the injection of fuel into the intake manifold immediately after opening the throttle may be omitted. It is important only that fuel is injected properly into the intake cylinder ZYL2 before it is ignited at restart.

FIG. 7 illustrates the choice of the speed threshold ns. Figure 7a illustrates the oscillation behavior of the intake cylinder ZYL2 at the correctly selected speed threshold value ns. At the opening crank shaft angle KWauf, the intake cylinder ZYL2 is in a forward movement, passes through the bottom dead center UT corresponding to the fourth dead center T4, and reverses at the return pendulum angle RPW. The further pendulum movement of the intake cylinder ZYL2 to standstill is in Figure 7a only hinted.

FIG. 7b illustrates the pendulum behavior of the intake cylinder ZYL2 at too high a selected speed threshold ns. Too high a speed threshold value ns means that the kinetic energy of the internal combustion engine when opening the throttle valve 100, ie at the opening crankshaft angle KWauf, is too high. As a result, the inlet cylinder ZYL2 passes through the bottom dead center UT corresponding to the fourth dead center T4 and subsequently also to the top dead center OT corresponding to the fifth dead center T5. This leads to undesirable Vibrations in the drive train, and is perceived by the driver as uncomfortable.

FIG. 7c illustrates the oscillation behavior of the intake cylinder ZYL2 when the speed threshold value ns selected is too low. Too low a threshold speed ns means that the kinetic energy of the internal combustion engine when opening the throttle valve 100, that is, at the opening crankshaft angle KWauf, is too low. The inlet cylinder ZYL2 passes through the bottom dead center UT corresponding to the fourth dead center, but has a relatively large return pendulum angle RPW. If it is determined in step 3020 that the rotational speed n of the internal combustion engine is greater than the rotational speed threshold value ns, it can no longer be reliably assumed that the intake cylinder ZYL2 rotates above the top dead center OT and the internal combustion engine can thus be started quickly.

The choice of the speed threshold value ns is thus of central importance to the functioning of the method according to the invention, but on the other hand is very difficult since it depends on variables which change during the service life of the internal combustion engine, such as the friction coefficient of the engine oil used.

FIG. 8 describes an adaptation method with which an initially predetermined speed threshold value ns can be adapted to compensate for errors in the initialization or changes in the characteristics of the internal combustion engine. In step 3000, it is determined that there is a stop request to the internal combustion engine, and measures for starting the internal combustion engine are initiated. In step 3010, it is checked in step 1030 whether the rotational speed n of the internal combustion engine has fallen below the rotational speed threshold ns. If so, step 3020 follows by opening the throttle in accordance with step 1040. It is followed by step 3030, in which it is checked whether the inlet cylinder ZYL2 has already passed through the bottom dead center UT. If not, step 3040 follows. If so, step 3060 follows.

In step 3040, the case is intercepted that the speed threshold value ns is set so low that the internal combustion engine comes to a stop before the intake cylinder ZYL2 passes through the bottom dead center UT. For this purpose is in step 3040 checks whether the internal combustion engine is stationary. If this is not the case, the method branches back to step 3030. If the internal combustion engine is present, step 3050 follows. In step 3050, the speed threshold value ns is increased. This is followed by step 3100, which ends the procedure.

In step 3060, the rotational movement of the internal combustion engine is monitored. If the internal combustion engine continues to rotate the inlet cylinder ZYL2 above the top dead center OT, step 3070 follows. If the top dead center OT is not reached, step 3080 follows. In step 3070, the in FIG. 7b illustrated behavior before, and the speed threshold ns is reduced. This is followed by step 3100, which ends the procedure.

In step 3080, the return angle RPW is determined using, for example, the crankshaft sensor 220. Step 3090 follows. In Step 3090, it is checked whether the return pendulum angle RPW is smaller than a minimum return pendulum angle RPWS which is, for example, 10 °. If the return pendulum angle RPW is smaller than the minimum return pendulum angle RPWS, then the proper behavior is according to Figure 7a and step 3100 follows, ending the procedure. If the return pendulum angle RPW is greater than the minimum return oscillation angle RPWS, then this is in FIG. 7c illustrated behavior, and it follows step 3050, in which the speed threshold value ns is increased.

The increase of the speed threshold ns in step 3050 may be either incremental, or the speed threshold ns is increased to an initial threshold nsi, at which it is ensured that the internal combustion engine is running in the FIG. 7b illustrated behavior shows that the speed threshold ns is then initially too large. The initial threshold value nsi can be designed, for example, as an applicable threshold value. It is chosen so that in the context of the possible during operation of the internal combustion engine operating parameters, for example, different leakage of the air filling, different engine oil or different specimen scattering of the friction effect of the internal combustion engine, the internal combustion engine in FIG. 7b illustrated behavior shows that so the intake cylinder ZYL2 goes into the power stroke.

The adaptation of the speed threshold value ns can optionally also be carried out if the restart of the internal combustion engine has not proceeded correctly: The speed threshold value ns is increased if it was decided in step 2020 that the determined speed n of the internal combustion engine is greater than the speed threshold value ns, and Performing steps 2030, 2040 and 2050 is determined in step 2060 that the inlet cylinder ZYL2 (ZYL2) has not gone into the power stroke.

Claims (13)

1. Method for stopping an internal combustion engine, in which a quantity of air supplied to the internal combustion engine via an air metering device, in particular a throttle valve (100), is reduced after a stop, request has been detected, wherein the quantity of air supplied to the internal combustion engine via the air metering device is increased again if a detected speed (n) of the internal combustion engine falls below a specifiable speed threshold value (ns), characterized in that an inlet cylinder (ZYL2), to which the quantity of air is supplied, still goes into its compression stroke, but no longer goes into a power stroke after the quantity of air supplied is increased.
2. Method according to Claim 1, characterized in that the speed threshold value (ns) is reduced if the inlet cylinder (ZYL2) goes into the power stroke after the quantity of air metered in is increased and before the internal combustion engine comes to a halt.
3. Method according to one of the preceding claims, characterized in that the speed threshold value is increased if the inlet cylinder (ZYL2) no longer goes into a compression stroke after the quantity of air metered in is increased.
4. Method according to one of the preceding claims, characterized in that the specifiable speed threshold value is modified in accordance with a reverse oscillation angle (RPW).
5. Method according to Claim 4, characterized in that the speed threshold value is increased if the reverse oscillation angle (RPW) is greater than a specifiable minimum reverse oscillation angle (RPWS).
6. Method according to either of Claims 4 and 5, characterized in that the specifiable speed threshold value (ns) is increased to a specifiable initial threshold value (nsi).
7. Method according to Claim 6, characterized in that the selected magnitude of the initial threshold value (nsi) is such that the inlet cylinder (ZYL2) passes through the top dead center position.
8. Method according to one of the preceding claims, characterized in that the quantity of air metered in by the air metering device is increased immediately after the closure of an outlet valve (160) of the inlet cylinder (ZYL2).
9. Method according to one of the preceding claims, characterized in that fuel is injected in such a way that an ignitable fuel/air mixture is present in the inlet cylinder (ZYL2) when it leaves the inlet stroke.
10. Method according to one of the preceding claims, characterized in that fuel is injected before or immediately after the inlet cylinder (ZYL2) goes into the inlet stroke.
11. Computer program, characterized in that it is programmed for use in a method according to one of Claims 1 to 10.
12. Electric storage medium for an open-loop and/or closed-loop control device for an internal combustion engine, characterized in that a computer program for use in a method according to Claims 1 to 10 is stored on said medium.
13. Ppen-loop and/or closed-loop control device for an internal combustion engine, characterized in that it is programmed for use in a method according to one of Claims 1 to 10.

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